Etching method

ABSTRACT

An etching method of etching a processing target object is provided. The processing target object has a supporting base body and a processing target layer. The processing target layer is provided on a main surface of the supporting base body and includes protrusion regions. Each protrusion region is extended upwards from the main surface, and an end surface of each protrusion region is exposed when viewed from above the main surface. The etching method includes a first process of forming a film on the end surface of each protrusion region; a second process of selectively exposing one or more end surfaces by anisotropically etching the film formed through the first process; and a third process of anisotropically etching the one or more end surfaces exposed through the second process atomic layer by atomic layer. The processing target layer contains silicon nitride, and the film contains silicon oxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2017-080798 filed on Apr. 14, 2017, the entire disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to an etching methodfor a processing target object.

BACKGROUND

In the field of semiconductor manufacture, it is required to form ahighly fine wiring pattern to meet a recent trend for miniaturization ofsemiconductor devices. To form this highly fine wiring pattern, anetching processing having high selectivity needs to be performed. PatentDocument 1 describes a technique regarding an etching method. In theetching method described in Patent Document 1, a mixed gas of a CH₃F gasand an O₂ gas is used as an etching gas for etching a silicon nitridefilm covering a silicon oxide film, and a mixing ratio (O₂/CH₃F) of theO₂ gas to the CH₃F gas in the mixed gas is set to be in the range from 4to 9. Patent Document 2 describes a technique regarding an etchingmethod of forming a spacer having multiple films. In the etching methoddisclosed in Patent Document 2, there is performed a multi-stageprocessing in which anisotropic etching is first performed on a low-kmaterial having high selectivity with respect to silicon nitride andisotropic etching is then performed on SiN having high selectivity withrespect to the low-k material. Further, Patent Document 3 discloses atechnique of forming a thin film using atomic layer deposition (ALD) orchemical vapor deposition (CVD).

Patent Document 1: Japanese Patent Laid-open Publication No. 2003-229418

Patent Document 2: Japanese Patent Laid-open Publication No. 2015-159284

Patent Document 3: US Patent Application Publication No. 2016/0163556

Patent Document 4: Japanese Patent Laid-open Publication No. 2012-505530

SUMMARY

In forming a complicated three-dimensional pattern having multiple endsurfaces (etching target surfaces) of different heights, assume thatonly a certain end surface among the multiple end surfaces isselectively etched anisotropically. In this case, if an etching gashaving relatively high deposition property is used, a deposit isgenerated at a region of a relatively high aspect ratio among grooves ofthe pattern formed by etching. If an etching gas having relatively lowdeposition property is used, on the other hand, etching having arelatively low selectivity is performed, so that the grooves of thepattern has non-uniform widths according to denseness and sparseness ofthe pattern. Thus, the three-dimensional pattern may not be formedsuccessfully due to these various problems. In this regard, there hasbeen a demand for a technique regarding anisotropic etching capable offorming the three-dimensional pattern successfully.

In an exemplary embodiment, there is provided an etching method ofetching a processing target object. The processing target object has asupporting base body and a processing target layer. The processingtarget layer is provided on a main surface of the supporting base bodyand includes protrusion regions. Each of the protrusion regions isextended upwards from the main surface, and an end surface of each ofthe protrusion regions is exposed when viewed from above the mainsurface. The etching method includes a first process of forming a filmon the end surface of each of the protrusion regions; a second processof selectively exposing one or more of the end surfaces byanisotropically etching the film formed through the first process; and athird process of anisotropically etching the one or more of the endsurfaces exposed through the second process atomic layer by atomiclayer. The processing target layer contains silicon nitride, and thefilm contains silicon oxide.

In this method, as for the protrusion regions each having the endsurface, the film is formed on each of the end surfaces through thefirst process, and only the film on one or more of the end surfaces isselectively removed through the second process. Then, through the thirdprocess, only the one or more of the end surfaces exposed by the removalof the film in the second process is anisotropically etched atomic layerby atomic layer. Accordingly, highly precise anisotropic etching can beperformed only on the one or more of the end surfaces among therespective end surfaces of the protrusion regions.

The film comprises a first film and a second film. The first processcomprises a fourth process of forming the first film conformally and afifth process of forming the second film on the first film. The secondfilm is formed in the fifth process such that a thickness of the secondfilm is increased as being distanced farther from the main surface.Since a thickness of the film formed by the first process differsdepending on a distance from the main surface of the supporting basebody, an end surface, on which the film is formed in a relatively thinthickness, is selectively exposed through the second process.

In the exemplary embodiment, the first film is conformally formed in thefourth process by repeating a first sequence comprising a sixth processof supplying a first gas into a space in which the processing targetobject is placed; a seventh process of purging, after the sixth process,the space in which the processing target object is placed; an eighthprocess of generating, after the seventh process, plasma of a second gasin the space in which the processing target object is placed; and aninth process of purging, after the eighth process, the space in whichthe processing target object is placed. The first gas contains anorganic-containing aminosilane-based gas, and the second gas containsoxygen atoms. Plasma of the first gas is not generated in the sixthprocess. A silicon oxide film having a uniform thickness is conformallyformed on each of the end surfaces of the protrusion regions of theprocessing target layer.

In the exemplary embodiment, the first gas contains monoaminosilane. Inthe sixth process, a reaction precursor of silicon is formed by usingthe first gas containing the monoaminosilane.

In the exemplary embodiment, the aminosilane-based gas contained in thefirst gas includes aminosilane having one to three silicon atoms.Further, the aminosilane-based gas contained in the first gas mayinclude aminosilane having one to three amino groups. The aminosilanehaving the one to three silicon atoms may be used as theaminosilane-based gas contained in the first gas. The aminosilane havingthe one to three amino groups may be used as the aminosilane-based gascontained in the first gas.

In the exemplary embodiment, in the fifth process, plasma of a third gasis generated in a space in which the processing target object is placed.The third gas contains silicon atoms and contains chlorine atoms orhydrogen atoms. The third gas includes a SiCl₄ gas or a SiH₄ gas. By theplasma of the third gas containing the silicon atoms and containing thechlorine atoms or the hydrogen atoms, for example, by the third gascontaining the SiCl₄ gas or the SiH₄ gas, the second film of the siliconoxide film can be additionally formed on the first film of the siliconoxide film which is conformally formed in the fourth process prior tothe fifth process.

In the exemplary embodiment, the second film is formed in the fifthprocess by repeating a second sequence comprising a tenth process ofsupplying a fourth gas into a space in which the processing targetobject is placed; an eleventh process of purging, after the tenthprocess, the space in which the processing target object is placed; atwelfth process of generating, after the eleventh process, plasma of afifth gas in the space in which the processing target object is placed;and a thirteenth process of purging, after the twelfth process, thespace in which the processing target object is placed. The fourth gascontains silicon atoms and chlorine atoms, and the fifth gas containsoxygen atoms. Plasma of the fourth gas is not generated in the tenthprocess. The fourth gas may include a mixed gas containing a SiCl₄ gasand an Ar gas. The second sequence including the tenth process using thefourth gas containing the silicon atoms and the chlorine atoms, forexample, the fourth gas containing the mixed gas containing the SiCl₄gas and the Ar gas and the twelfth process using the plasma of the fifthgas containing the oxygen atoms is repeatedly performed, so that thesecond film of the silicon oxide film can be additionally formed on thefirst film of the silicon oxide film which is conformally formed in thefourth process prior to the fifth process.

In the exemplary embodiment, in the second process, plasma of a sixthgas is generated in a space in which the processing target object isplaced and a bias power is applied to the plasma of the sixth gas. Thesixth gas contains a fluorocarbon-based gas. The end surface, on whichthe film is formed in the relatively thin thickness, is selectivelyexposed by the anisotropic etching using the plasma of thefluorocarbon-based gas.

In the exemplary embodiment, the one or more of the end surfaces exposedthrough the second process are removed atomic layer by atomic layer tobe selectively and anisotropically etched by repeating a third sequencecomprising a fourteenth process of generating plasma of a seventh gas ina space in which the processing target object is placed and forming amixed layer containing ions included in the plasma of the seventh gas onan atomic layer of the one or more of the end surfaces exposed throughthe second process, a fifteenth process of purging, after the fourteenthprocess, the space in which the processing target object is placed, asixteenth process of generating, after the fifteenth process, plasma ofan eighth gas in the space in which the processing target object isplaced and removing the mixed layer by radicals included in the plasmaof the eighth gas; and a seventeenth process of purging, after thesixteenth process, the space in which the processing target object isplaced. The seventh gas contains hydrogen atoms or oxygen atoms, and theeighth gas contains fluorine atoms. The end surface exposed through thesecond process is modified atomic layer by atomic layer, so that themixed layer is formed in the fourteenth process. Further, the region(the mixed layer) modified through the fourteenth process can be removedin the sixteenth process. Accordingly, as the third sequence includingthe fourteenth process and the sixteenth process is repeated, the endsurface exposed through the second process can be selectively etched toa required extent.

In the exemplary embodiment, in the fourteenth process, by applying abias power to the plasma of the seventh gas, the mixed layer containingthe ions is formed on the atomic layer of the one or more of the endsurfaces exposed through the second process. In the fourteenth process,by applying the bias power to the seventh gas, the mixed layer isselectively formed on the atomic layer of the end surface exposedthrough the second process.

In the exemplary embodiment, the eighth gas includes a mixed gascontaining a NF₃ gas and an O₂ gas. The mixed layer formed through thefourteenth process is removed by using the plasma of the eighth gascontaining the mixed gas of the NF₃ gas and the O₂ gas.

As stated above, it is possible to provide the technique regarding theanisotropic etching capable of forming the three-dimensional patternsuccessfully.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1 is a flowchart for describing a method according to an exemplaryembodiment;

FIG. 2 is a diagram illustrating an example of a plasma processingapparatus;

FIG. 3 is a cross sectional view schematically illustrating a state ofmajor portions of a surface of a wafer before the method shown in FIG. 1is performed;

FIG. 4 is a cross sectional view schematically illustrating a state ofthe major portions of the surface of the wafer while the method shown inFIG. 1 is being performed;

FIG. 5 is a cross sectional view schematically illustrating a state ofthe major portions of the surface of the wafer while the method shown inFIG. 1 is being performed;

FIG. 6 is a cross sectional view schematically illustrating a state ofthe major portions of the surface of the wafer while the method shown inFIG. 1 is being performed;

FIG. 7 is a cross sectional view schematically illustrating a state ofthe major portions of the surface of the wafer while the method shown inFIG. 1 is being performed;

FIG. 8 is a cross sectional view schematically illustrating a state ofthe major portions of the surface of the wafer after the method shown inFIG. 1 is performed;

FIG. 9 presents a flowchart for describing a process of a part of themethod shown in FIG. 1 in further detail;

FIG. 10A and FIG. 10B are flowcharts for describing a process of a partof the method shown in FIG. 1 in further detail;

FIG. 11 is a flowchart for describing a process of a part of the methodshown in FIG. 1 in further detail;

FIG. 12A to FIG. 12C are diagrams schematically illustrating a principleof film formation performed in the method shown in FIG. 1; and

FIG. 13A to FIG. 13C are diagrams schematically illustrating a principleof etching performed in the method shown in FIG. 1.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current exemplary embodiment. Still, theexemplary embodiments described in the detailed description, drawings,and claims are not meant to be limiting. Other embodiments may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the drawings, may bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

Hereinafter, various exemplary embodiments of the present disclosurewill be explained in detail with reference to the accompanying drawings.In the various drawings, same or corresponding parts will be assignedsame reference numerals. Now, an etching method (method MT) which can beperformed by using a plasma processing apparatus 10 will be explainedwith reference to FIG. 1. FIG. 1 is a flowchart for describing themethod according to an exemplary embodiment. The method MT according tothe exemplary embodiment shown in FIG. 1 is an example of the etchingmethod upon a processing target object (hereinafter, sometimes referredto as “wafer”).

In the method MT according to the exemplary embodiment, a series ofprocesses can be performed by using a single plasma processingapparatus. FIG. 2 is a diagram illustrating an example of the plasmaprocessing apparatus. FIG. 2 schematically illustrates a cross sectionalconfiguration of the plasma processing apparatus 10 which can be used invarious exemplary embodiments of a method of processing a processingtarget object. As depicted in FIG. 2, the plasma processing apparatus 10is configured as a plasma etching apparatus having parallel plate typeelectrodes and includes a processing vessel 12. The processing vessel 12has a substantially cylindrical shape. The processing vessel 12 is madeof, by way of example, but not limitation, aluminum, and an inner wallsurface of the processing vessel 12 is anodically oxidized. Theprocessing vessel 12 is frame-grounded.

A substantially cylindrical supporting member 14 is provided on a bottomportion of the processing vessel 12. The supporting member 14 is madeof, by way of example, but not limitation, an insulating material. Theinsulating material forming the supporting member 14 may contain oxygen,such as quartz. Within the processing vessel 12, the supporting member14 is vertically extended from the bottom portion of the processingvessel 12. A mounting table PD is provided within the processing vessel12. The mounting table PD is supported by the supporting member 14.

The mounting table PD is configured to hold the wafer W on a top surfacethereof. The mounting table PD includes a lower electrode LE and anelectrostatic chuck ESC. The lower electrode LE is provided with a firstplate 18 a and a second plate 18 b. The first plate 18 a and the secondplate 18 b are made of a metal such as, but not limited to, aluminum andhave a substantially disk shape. The second plate 18 b is provided onthe first plate 18 a and electrically connected with the first plate 18a.

The electrostatic chuck ESC is provided on the second plate 18 b. Theelectrostatic chuck ESC includes a pair of insulating layers orinsulating sheets; and an electrode embedded therebetween. The electrodeof the electrostatic chuck ESC is electrically connected to a DC powersupply 22 via a switch 23. The electrostatic chuck ESC is configured toattract the wafer W by an electrostatic force such as a Coulomb forcegenerated by a DC voltage applied from the DC power supply 22.Accordingly, the electrostatic chuck ESC is capable of holding the waferW.

A focus ring FR is provided on a peripheral portion of the second plate18 b to surround an edge of the wafer W and the electrostatic chuck ESC.The focus ring FR is configured to improve etching uniformity. The focusring FR is made of a material which is appropriately selected dependingon a material of an etching target film. For example, the focus ring FRmay be made of quartz.

A coolant path 24 is provided within the second plate 18 b. The coolantpath 24 constitutes a temperature control mechanism. A coolant issupplied into the coolant path 24 from a chiller unit (not shown)provided outside the processing vessel 12 via a pipeline 26 a. Thecoolant supplied into the coolant path 24 is then returned back into thechiller unit via a pipeline 26 b. In this way, the coolant is suppliedto be circulated through the coolant path 24. A temperature of the waferW held by the electrostatic chuck ESC is controlled by adjusting atemperature of the coolant.

The plasma processing apparatus 10 is provided with a gas supply line28. Through the gas supply line 28, a heat transfer gas, e.g., a He gas,is supplied from a heat transfer gas supply device into a gap between atop surface of the electrostatic chuck ESC and a rear surface of thewafer W.

The plasma processing apparatus 10 is also equipped with a heater HT asa heating device. The heater HT is embedded in, for example, the secondplate 18 b, and is connected to a heater power supply HP. As a power issupplied to the heater HT from the heater power supply HP, thetemperature of the mounting table PD is adjusted so that the temperatureof the wafer W placed on the mounting table PD is adjusted.Alternatively, the heater HT may be embedded in the electrostatic chuckESC.

The plasma processing apparatus 10 includes an upper electrode 30. Theupper electrode 30 is provided above the mounting table PD, facing themounting table PD. The lower electrode LE and the upper electrode 30 arearranged to be substantially parallel to each other. Provided betweenthe upper electrode 30 and the lower electrode LE is a processing spaceS in which a plasma processing is performed on the wafer W.

The upper electrode 30 is supported at an upper portion of theprocessing vessel 12 with an insulating shield member 32 therebetween.The insulating shield member 32 is made of an insulating material, suchas quartz, containing oxygen. The upper electrode 30 may include anelectrode plate 34 and an electrode supporting body 36. The electrodeplate 34 faces the processing space S, and is provided with a multiplenumber of gas discharge holes 34 a. In the exemplary embodiment, theelectrode plate 34 contains silicon. In another exemplary embodiment,the electrode plate 34 may contain silicon oxide.

The electrode supporting body 36 is configured to support the electrodeplate 34 in a detachable manner, and is made of a conductive materialsuch as, but not limited to, aluminum. The electrode supporting body 36may have a water-cooling structure. A gas diffusion space 36 a is formedwithin the electrode supporting body 36. A multiple number of gasthrough holes 36 b are extended downwards from the gas diffusion space36 a to communicate with the gas discharge holes 34 a, respectively. Theelectrode supporting body 36 is provided with a gas inlet opening 36 cthrough which a gas is introduced into the gas diffusion space 36 a, anda gas supply line 38 is connected to the gas inlet opening 36 c.

The gas supply line 38 is connected to a gas source group 40 via a valvegroup 42 and a flow rate control unit group 44. The gas source group 40includes a plurality of gas sources. Examples of the plurality of gassources according to the exemplary embodiment are described below, butnot limited thereto. These gas sources include a source of anorganic-containing aminosilane-based gas, a source of afluorocarbon-based gas (C_(x)F_(y) gas (x and y denote integers rangingfrom 1 to 10)), a source of a gas having an oxygen atom (e.g., an oxygengas, etc.), a source of a NF₄ gas, a source of a hydrogen-containing gas(e.g., a hydrogen gas, a SiH₄ gas, etc.) and a source of a rare gas(e.g., an Ar gas, etc.). The fluorocarbon-based gas may be, by way ofexample, a CF₄ gas, a C₄F₆ gas, a C₄F₈ gas, or the like. As theaminosilane-based gas, one having a molecular structure, which containsa relatively small number of amino groups, may be used. For example,monoaminosilane (H₃—Si—R (R denotes an amino group which containsorganic and can be substituted)) may be used. Further, theaforementioned aminosilane-based gas (a gas contained in a first gas G1to be described later) may contain aminosilane having one to threesilicon atoms or aminosilane having one to three amino groups. Theaminosilane having the one to three silicon atoms may be monosilane(monoaminosilane) having one to three amino groups, disilane having oneto three amino groups, or trisilane having one to three amino groups.Further, the aforementioned aminosilane may have an amino group whichcan be substituted. Further, the aforementioned amino group may besubstituted by one of a methyl group, an ethyl group, a propyl group ora butyl group. Further, the methyl group, the ethyl group, the propylgroup or the butyl group may be substituted by halogen. Any of variousrare gases such as an Ar gas and a He gas may be used as the rare gas.

The valve group 42 includes a plurality of valves, and the flow ratecontrol unit group 44 includes a plurality of flow rate control unitssuch as mass flow controllers. Each of the plurality of gas sources ofthe gas source group 40 is connected to the gas supply line 38 via acorresponding valve of the valve group 42 and a corresponding flow ratecontrol unit of the flow rate control unit group 44. Accordingly, theplasma processing apparatus 10 is capable of supplying gases into theprocessing vessel 12 from one or more gas sources selected from theplurality of gas sources of the gas source group 40 at individuallycontrolled flow rates.

In the plasma processing apparatus 10, a deposition shield 46 isdetachably provided along an inner wall of the processing vessel 12. Thedeposition shield 46 is also provided on an outer side surface of thesupporting member 14. The deposition shield 46 is configured to suppressan etching byproduct (deposit) from adhering to the processing vessel12, and may be formed of an aluminum member coated with ceramics such asY₂O₃. The deposition shield may be made of a material containing oxygen,such as quartz, besides Y₂O₃.

At the bottom portion of the processing vessel 12, a gas exhaust plate48 is provided between the supporting member 14 and the sidewall of theprocessing vessel 12. The gas exhaust plate 48 may be made of, by way ofexample, an aluminum member coated with ceramic such as Y₂O₃. Theprocessing vessel 12 is also provided with a gas exhaust opening 12 eunder the gas exhaust plate 48, and the gas exhaust opening 12 e isconnected with a gas exhaust device 50 via a gas exhaust line 52. Thegas exhaust device 50 has a vacuum pump such as a turbo molecular pumpand is capable of decompressing the processing space S of the processingvessel 12 to a required vacuum level. A carry-in/out opening 12 g forthe wafer W is provided at the sidewall of the processing vessel 12, andthe carry-in/out opening 12 g is opened/closed by a gate valve 54.

The plasma processing apparatus 10 further includes a first highfrequency power supply 62 and a second high frequency power supply 64.The first high frequency power supply 62 is configured to generate afirst high frequency power for plasma generation having a frequencyranging from 27 MHz to 100 MHz, e.g., 60 MHz. The first high frequencypower supply 62 is connected to the upper electrode 30 via a matchingdevice 66. The matching device 66 is a circuit configured to match anoutput impedance of the first high frequency power supply 62 and aninput impedance at a load side (lower electrode LE side). Further, thefirst high frequency power supply 62 may be connected to the lowerelectrode LE via the matching device 66.

The second high frequency power supply 64 is configured to generate asecond high frequency power for ion attraction into the wafer W. Forexample, the second high frequency power supply 64 generates a highfrequency bias power having a frequency ranging from 400 kHz to 40.68MHz, e.g., 13.56 MHz. The second high frequency power supply 64 isconnected to the lower electrode LE via a matching device 68. Thematching device 68 is a circuit configured to match an output impedanceof the second high frequency power supply 64 and the input impedance atthe load side (lower electrode LE side).

The plasma processing apparatus 10 further includes a power supply 70.The power supply 70 is connected to the upper electrode 30. The powersupply 70 applies to the upper electrode 30 a voltage for attractingpositive ions existing in the processing space S into the electrodeplate 34. As an example, the power supply 70 is a DC power supplyconfigured to generate a negative DC voltage. If this voltage is appliedto the upper electrode 30 from the power supply 70, the positive ionsexisting in the processing space S collide with the electrode plate 34.As a result, secondary electrons and/or silicon is released from theelectrode plate 34.

In the exemplary embodiment, the plasma processing apparatus 10 furtherincludes a control unit Cnt. The control unit Cnt is implemented by acomputer including a processor, a storage unit, an input device, adisplay device, and so forth, and is configured to control theindividual components of the plasma processing apparatus 10. To bespecific, the control unit Cnt is connected to the valve group 42, theflow rate control unit group 44, the gas exhaust device 50, the firsthigh frequency power supply 62, the matching device 66, the second highfrequency power supply 64, the matching device 68, the power supply 70,the heater power supply HP and the chiller unit.

The control unit Cnt is operated to output a control signal according toa program based on an input recipe. Selection of the gas supplied fromthe gas source group 40 and a flow rate of the selected gas, the gasexhaust by the gas exhaust device 50, the power supplies from the firsthigh frequency power supply 62 and the second high frequency powersupply 64, the voltage application from the power supply 70, the powersupply of the heater power supply HP, and the control of the flow rateand the temperature of the coolant from the chiller unit can be achievedin response to control signals from the control unit Cnt. Further,individual processes of the method MT of processing the processingtarget object in the preset specification can be carried out as theindividual components of the plasma processing apparatus 10 are operatedunder the control by the control unit Cnt.

Referring back to FIG. 1, the explanation of the method MT will becarried on. In the following description, reference is made to FIG. 2 toFIG. 13C as well as FIG. 1. Major structure of the wafer W prepared in aprocess ST1 of the method MT shown in FIG. 1 will be explained withreference to FIG. 3. The wafer W prepared in the process ST1 is shown inFIG. 3. The wafer W depicted in FIG. 3 has a supporting base body BE anda processing target layer EL. The processing target layer EL is providedon a main surface BE1 of the supporting base body BE. The main surfaceBE1 is extended to be perpendicular to a surface-perpendicular directionDR. The surface-perpendicular direction DR corresponds to a verticaldirection in a state that the wafer W is placed on the electrostaticchuck ESC, as shown in FIG. 2.

The processing target layer EL has a plurality of protrusion regions(e.g., a protrusion region PJ1, a protrusion region PJ2, etc.). Each ofthe plurality of protrusion regions of the processing target layer EL isextended upwards from the main surface BE1. Each of the plurality ofprotrusion regions of the processing target layer EL has an end surface.The protrusion region PJ1 has an end surface TE1. The protrusion regionPJ2 has an end surface TE2. The end surfaces of the individualprotrusion regions of the processing target layer EL are exposed whenviewed from above the main surface BE1. The end surface TE1 of theprotrusion region PJ1 and the end surface TE2 of the protrusion regionPJ2 are all exposed when viewed from above the main surface BEL

A height of the protrusion region is a distance from the main surfaceBE1 to an end surface of the corresponding protrusion region. A heightTT1 of the protrusion region PJ1 is a distance from the main surface BE1to the end surface TE1. A height TT2 of the protrusion region PJ2 is adistance from the main surface BE1 to the end surface TE2. Theindividual protrusion regions of the processing target layer EL may havedifferent heights. The protrusion region PJ1 has a lower height than theprotrusion region PJ2 (a value of the height TT1 of the protrusionregion PJ1 is smaller than a value of the height TT2 of the protrusionregion PJ2).

The supporting base body BE is made of, by way of example, but notlimitation, a material containing Si (silicon). The material of theprocessing target layer EL may contain, by way of non-limiting example,silicon nitride (e.g., SiN) or the like. In the present exemplaryembodiment, the processing target layer EL is made of SiN. However, theexemplary embodiment is not limited thereto, and the processing targetlayer EL may be made of a material other than the silicon nitride. To bespecific, the wafer W may be a substrate product for use in forming, forexample, a FinFET (Fin Field Effect Transistor). In this case, theprotrusion region PJ1 of the wafer W corresponds to a fin region of theFinFET, and the protrusion region PJ2 of the wafer W corresponds to agate electrode of the FinFET. The fin region includes a drain electrodeand a source electrode, and is extended to intersect the gate electrode.The drain electrode is provided at one end of the fin region, and thesource electrode is provided at the other end of the fin region.

End portions (regions including end surfaces such as the end surfaceTE1, the end surface TE2, and so forth) of the plurality of protrusionregions (the protrusion region PJ1, the protrusion region PJ2, and soforth) may have a shape which is narrowed toward tips thereof (tapershape). In this case, in each of the protrusion regions, a width of theend surface (the end surface TE1, the end surface TE2, or the like) isshorter than a width of a basal end side (a side close to the supportingbase body BE). In case that each protrusion region of the processingtarget layer EL has the shape which is narrowed toward the tip thereof,a width of an opening formed and confined by the end portion of eachprotrusion region is relatively enlarged, so that formation of a depositon the end portion of each protrusion region can be suppressedsufficiently.

After the process ST1, a process (first process) of forming a film oneach of the end surfaces of the protrusion regions (including theprotrusion region PJ1 and the protrusion region PJ2) of the processingtarget layer EL is performed in the state that the wafer W is placed onthe electrostatic chuck ESC, as illustrated in FIG. 2. The correspondingprocess includes a process ST2 (including the first process and a fourthprocess) and a process ST3 (including the first process and a fifthprocess) shown in FIG. 1, and the corresponding film includes a firstfilm SF1 and a second film SF2 to be described later. As an example, thecorresponding film may contain silicon oxide (e.g., a SiO₂ film), or maycontain another material (e.g., SiN, a metal, or the like) other thanthe silicon oxide.

In the process ST2 following the process ST1, the first film SF1 isconformally formed on a surface EL1 of the processing target layer EL(particularly, on the end surfaces of the respective protrusion regionsof the processing target layer EL) in the state that the wafer W isplaced on the electrostatic chuck ESC as depicted in FIG. 2. Details ofthe process ST2 are shown in FIG. 9. As shown in FIG. 9, the process ST2includes a process ST2 a (sixth process), a process ST2 b (seventhprocess), a process ST2 c (eighth process), a process ST2 d (ninthprocess), and a process ST2 e. The processes ST2 a to ST2 d constitute asequence SQ1 (first sequence). In the process ST2, the sequence SQ1 isperformed one or more times. The sequence SQ1 and the process ST2 e areprocesses of conformally forming the first film SF1 of silicon oxide(e.g., SiO₂ film) on the surface EL1 of the processing target layer EL,as shown in FIG. 4, through the same method as an ALD (Atomic LayerDeposition) method. As a result of performing the series of processesfrom the sequence SQ1 to the process ST2 e, the first film SF1 having afilm thickness controlled with high accuracy is conformally formed onthe surface of the wafer W (particularly, on the surface EL1 of theprocessing target layer EL). Hereinafter, as the exemplary embodiment,details of the process ST2 performed when the first film SF1 includesthe silicon oxide (e.g., the SiO₂ film) will be explained. If, however,the first film SF1 contains a film of another material besides thesilicon oxide film containing the silicon oxide, other kinds of gases aswell as gas kinds specified below may be used.

In the process ST2 a, the first gas G1 is supplied into the processingspace S of the processing vessel 12 in which the wafer W is placed. Toelaborate, in the process ST2 a, the first gas G1 is introduced into theprocessing space S of the processing vessel 12, as illustrated in FIG.12A. The first gas G1 includes an organic-containing aminosilane-basedgas. The first gas G1 composed of the organic-containingaminosilane-based gas is supplied into the processing space S of theprocessing vessel 12 from a gas source selected from the plurality ofgas sources belonging to the gas source group 40. For example,monoaminosilane (H₃—Si—R (R denotes an organic-containing amino group))may be used as the organic-containing aminosilane-based gas of the firstgas G1. In the process ST2 a, plasma of the first gas G1 is notgenerated.

Molecules of the first gas G1 adhere to the surface of the wafer W(including the surface EL1 of the processing target layer EL) as areaction precursor (layer Ly1), as shown in FIG. 12B. The molecules ofthe first gas G1 (monoaminosilane) adhere to the surface EL1 of theprocessing target layer EL by chemical adsorption caused by chemicalbond, and no plasma is used. Other than the monoaminosilane, any ofvarious types of gases may be used as long as the gas can be attached tothe surface EL1 of the processing target layer EL by the chemical bondand contains silicon. The aminosilane-based gas contained in the firstgas G1 may include, besides the monoaminosilane, aminosilane having oneto three silicon atoms. Further, the aminosilane-based gas contained inthe first gas G1 may include aminosilane having one to three aminogroups.

As stated above, since the first gas G1 contains the organic-containingaminosilane-based gas, the reaction precursor of the silicon (layer Ly1)is formed on the surface of the wafer W along an atomic layer of thesurface of the wafer W in the process ST2 a.

In the process ST2 b following the process ST2 a, the processing space Sof the processing vessel 12 is purged. To elaborate, the first gas G1supplied in the process ST2 a is exhausted. In the process ST2 b, aninert gas such as a nitrogen gas or a rare gas (e.g., Ar gas or thelike) may be supplied into the processing vessel 12 as a purge gas. Thatis, the purging of the process ST2 b may be implemented by a gas purgingof allowing the inert gas to flow in the processing space S of theprocessing vessel 12 or a purging by vacuum evacuation. In the processST2 b, excess molecules attached on the wafer W can be also removed.Through the above-described processes, the layer Ly1 of the reactionprecursor is formed to be a very thin monomolecular layer.

In the process ST2 c following the process ST2 b, plasma P1 of a secondgas is generated in the processing space S of the processing vessel 12,as illustrated in FIG. 12B. The second gas includes a gas containingoxygen atoms. For example, the second gas may contain an oxygen gas. Thesecond gas including the gas containing the oxygen atoms is suppliedinto the processing space S of the processing vessel 12 from a gassource selected from the plurality of gas sources belonging to the gassource group 40. Then, the high frequency power is supplied from thefirst high frequency power supply 62. In this case, the bias power mayalso be applied from the second high frequency power supply 64.Furthermore, it may also be possible to generate the plasma by usingonly the second high frequency power supply 64 without using the firsthigh frequency power supply 62. By operating the gas exhaust device 50,an internal pressure of the processing space S of the processing vessel12 is set to a predetermined pressure. As a result, the plasma P1 of thesecond gas is generated in the processing space S of the processingvessel 12. As depicted in FIG. 12B, if the plasma P1 of the second gasis generated, active species of oxygen, for example, oxygen radials aregenerated, so that a layer Ly2 of a silicon oxide film (corresponding tothe first film SF1) is formed as a monomolecular layer, as shown in FIG.12C.

As stated above, since the second gas contains the oxygen atoms, in theprocess ST2 c, the corresponding oxygen atoms combine with the reactionprecursor (layer Ly1), so that the layer Ly2 of the silicon oxide filmcan be conformally formed. Thus, the same as in the ALD method, byperforming the sequence SQ1 a single time (unit cycle), the layer Ly2 ofthe silicon oxide film can be conformally formed on the surface of thewafer W.

In the process ST2 d following the process ST2 c, the processing space Sof the processing vessel 12 is purged. To elaborate, the second gassupplied in the process ST2 c is exhausted. In the process ST2 d, aninert gas such as a nitrogen gas or a rare gas (e.g., Ar gas or thelike) may be supplied into the processing vessel 12 as a purge gas. Thatis, the purging of the process ST2 d may be implemented by the gaspurging of allowing the inert gas to flow in the processing space S ofthe processing vessel 12 or the purging by vacuum evacuation.

In the process ST2 e following the sequence SQ1, it is determinedwhether or not to finish the repetition of the sequence SQ1. Toelaborate, in the process ST2 e, it is determined whether the repetitionnumber of the sequence SQ1 has reached a preset number. A thickness ofthe first film SF1 formed on the surface EL1 of the processing targetlayer EL shown in FIG. 4 relies on the repetition number of the sequenceSQL That is, the thickness of the first film SF1 finally formed on thesurface EL1 of the processing target layer EL is substantiallydetermined by a product of the repetition number of the sequence SQ1 anda thickness of the silicon oxide film formed by performing the sequenceSQ1 a single time (unit cycle). Thus, the repetition number of thesequence SQ1 may be set based on a required thickness of the first filmSF1 formed on the surface EL1 of the processing target layer EL. As thesequence SQ1 is carried out repeatedly as stated above, the first filmSF1 of the silicon oxide film is conformally formed on the surface EL1of the processing target layer EL.

If it is determined in the process ST2 e that the repetition number ofthe sequence SQ1 has not reached the preset number (process ST2 e: NO),the sequence SQ1 is repeated. If, on the other hand, it is determined inthe process ST2 e that the repetition number of the sequence SQ1 hasreached the preset number (process ST2 e: YES), the sequence SQ1 isended. As a result, as shown in FIG. 4, the first film SF1 of thesilicon oxide film is formed on the surface EL1 of the processing targetlayer EL. That is, as the sequence SQ1 is repeatedly performed thepreset number of times, the first film SF1 having the required thicknessis conformally formed on the surface EL1 of the processing target layerEL. The thickness of the first film SF1 can be controlled with highaccuracy by repeating the sequence SQ1. As described above, in theseries of processes of the sequence SQ1 and the process ST2 e, the firstfilm SF1 can be conformally formed on the surface EL1 of the processingtarget layer EL through the same method as the ALD method.

In the process ST3 following the process ST2, a second film SF2 made ofthe same material as the first film SF1 is formed on the first film SF1formed in the process ST2 in the state that the wafer W is placed on theelectrostatic chuck ESC, as shown in FIG. 2. In the process ST3, thesecond film SF2 is formed such that a thickness thereof increases as itis distanced farther from the main surface BE1 of the supporting basebody BE. To be more specific, through the process ST3, the second filmSF2 is formed on the first film SF1, specifically, on the individual endsurfaces of the protrusion regions of the processing target layer EL(the end surface TE1 of the protrusion region PJ1, the end surface TE2of the protrusion region PJ2, etc.), as depicted in FIG. 5. The filmformation of the process ST3 is achieved through a process ST31 (fifthprocess) shown in FIG. 10A or a process ST32 (fifth process) shown inFIG. 10B. The process ST31 shown in FIG. 10A is an example of theprocess ST3, and the process ST32 shown in FIG. 10B is another exampleof the process ST3.

The second film SF2 is made of the same material as the first film SF1.As depicted in FIG. 5, a thickness TH1 of a portion of the second filmSF2 formed on the end surface TE1 of the protrusion region PJ1 issmaller than a thickness TH2 a of a portion of the second film SF2formed on the end surface TE2 of the protrusion region PJ2. A distancebetween the end surface TE1 of the protrusion region PJ1 and the mainsurface BE1 of the supporting base body BE (that is, the height TT1 ofthe protrusion region PJ1) is shorter than a distance between the endsurface TE2 of the protrusion region PJ2 and the main surface BE1 of thesupporting base body BE (that is, the height TT2 of the protrusionregion PJ2). As stated, in the film formation of the process ST3, thethickness of the film being formed can be controlled depending on thedistance from the main surface BE1 of the supporting base body BE (theheight of the protrusion region). On the protrusion regions (includingthe protrusion region PJ1 and the protrusion region PJ2) of theprocessing target layer EL provided on the main surface BE1 of thesupporting base body BE, the higher the height from the main surface BE1of the supporting base body BE is, the larger the thickness of thesecond film SF2 formed on the individual end surfaces of the protrusionregions (the end surface TE1 of the protrusion region PJ1, the endsurface TE2 of the protrusion region PJ2, etc.) is.

The example case where the film formation of the process ST3 is achievedby the process ST31 shown in FIG. 10A will be explained. Here, as theexemplary embodiment, details of the process ST31 which is performedwhen the first film SF1 and the second film SF2 contain the siliconoxide (e.g., the SiO₂ film) will be described. However, when the firstfilm SF1 and the second film SF2 contain a film of another materialbesides the silicon oxide film containing the silicon oxide, other kindsof gases as well as gas kinds specified below may also be used. Theprocess ST31 includes a process ST31 a and a process ST31 b. In theprocess ST31 a, a third gas is supplied into the processing space S ofthe processing vessel 12 from a gas source selected from the pluralityof gas sources belonging to the gas source group 40. The third gascontains silicon atoms and, also, contains chlorine atoms or hydrogenatoms. The third gas contains a SiCl₄ gas or a SiH₄gas. By way ofnon-limiting example, the third gas may be a mixed gas containing theSiCl₄ gas, an Ar gas and an oxygen gas. In the third gas, the SiCl₄ gasmay be replaced with the SiH₄ gas. The high frequency power is suppliedfrom the first high frequency power supply 62 and the high frequencybias power is supplied form the second high frequency power supply 64,and the internal pressure of the processing space S of the processingvessel 12 is set to a predetermined pressure by operating the gasexhaust device 50. As a result, plasma of the third gas is generated inthe processing space S of the processing vessel 12 in which the wafer Wis placed.

Now, another example where the film formation of the process ST3 isimplemented by the process ST32 shown in FIG. 10B will be explained. Asshown in FIG. 10B, the process ST32 includes a process ST32 a (tenthprocess), a process ST32 b (eleventh process), a process ST32 c (twelfthprocess), a process ST32 d (thirteenth process) and a process ST32 e.The processes ST32 a to ST32 d constitute a sequence SQ2 (secondsequence). In the process ST32, the sequence SQ2 is performed one ormore times. The sequence SQ2 and the process ST32 e are processes offorming the second film SF2 on the first film SF1 by a similar method tothe process ST2. As the series of processes from the sequence SQ2 to theprocess ST32 e are performed, the second film SF2 made of the samematerial as the first film SF1 is formed on the first film SF1 (morespecifically, on the individual end surfaces of the protrusion regionsof the processing target layer EL (the end surface TE1 of the protrusionregion PJ1, the end surface TE2 of the protrusion region PJ2, and soforth)). Here, as the exemplary embodiment, details of the process ST32which is performed when the first film SF1 and the second film SF2contain the silicon oxide (e.g., the SiO₂ film) will be described.However, when the first film SF1 and the second film SF2 contain a filmof another material besides the silicon oxide film containing thesilicon oxide, other kinds of gases as well as gas kinds specified belowmay also be used.

In the process ST32 a, a fourth gas G4 is supplied into the processingspace S of the processing vessel 12. To elaborate, in the process ST32a, the fourth gas G4 is introduced into the processing space S of theprocessing vessel 12, as illustrated in FIG. 12A. In the process ST32 a,the fourth gas G4 is supplied into the processing space S of theprocessing vessel 12 from a gas source selected from the plurality ofgas sources belonging to the gas source group 40. The fourth gas G4contains silicon atoms and chlorine atoms. The fourth gas G4 may be amixed gas containing, but not limited to, a SiCl₄ gas and an Ar gas. Inthe process ST32 a, plasma of the fourth gas G4 is not generated.Molecules of the fourth gas G4 adhere to the surface of the wafer W(including the surface EL1 of the processing target layer EL) as areaction precursor (layer Ly1), as shown in FIG. 12B.

In the process ST32 b following the process ST32 a, the processing spaceS of the processing vessel 12 is purged. To elaborate, the fourth gas G4supplied in the process ST32 a is exhausted. In the process ST32 b, aninert gas such as a nitrogen gas or a rare gas (e.g., Ar gas or thelike) may be supplied into the processing vessel 12 as a purge gas. Thatis, the purging of the process ST32 b may be implemented by the gaspurging of allowing the inert gas to flow in the processing space S ofthe processing vessel 12 or the purging by vacuum evacuation. In theprocess ST32 b, excess molecules attached on the wafer W can be alsoremoved.

In the process ST32 c following the process ST32 b, plasma P2 of a fifthgas is generated in the processing space S of the processing vessel 12,as depicted in FIG. 12B. The fifth gas is supplied into the processingspace S of the processing vessel 12 from a gas source selected from theplurality of gas sources belonging to the gas source group 40. The fifthgas contains oxygen atoms. The fifth gas may be a mixed gas containing,by way of example, but not limitation, an oxygen gas and an Ar gas. Thehigh frequency power is supplied from the first high frequency powersupply 62. In this case, the bias power from the second high frequencypower supply 64 may be applied. Further, it may be also possible togenerate the plasma by using only the second high frequency power supply64 without using the first high frequency power supply 62. The internalpressure of the processing space S of the processing vessel 12 is set toa predetermined pressure by operating the gas exhaust device 50. As aresult, the plasma P2 of the fifth gas is generated in the processingspace S of the processing vessel 12. If the plasma P2 of the fifth gasis generated as shown in FIG. 12B, active species of oxygen, forexample, oxygen radicals are generated, so that a layer Ly2 of thesilicon oxide film (corresponding to the second film SF2) is formed, asshown in FIG. 12C. Thus, as in the process ST2, by performing thesequence SQ2 a single time (unit cycle), the layer Ly2 of the siliconoxide film can be formed on the first film SF1.

In the process ST32 d following the process ST32 c, the processing spaceS of the processing vessel 12 is purged. To elaborate, the fifth gassupplied in the process ST32 c is exhausted. In the process ST32 d, aninert gas such as a nitrogen gas or a rare gas (e.g., Ar gas or thelike) may be supplied into the processing vessel 12 as a purge gas. Thatis, the purging of the process ST32 d may be implemented by the gaspurging of allowing the inert gas to flow in the processing space S ofthe processing vessel 12 or the purging by vacuum evacuation.

In the process ST32 e following the sequence SQ2, it is determinedwhether or not to finish the repetition of the sequence SQ2. Toelaborate, in the process ST32 e, it is determined whether therepetition number of the sequence SQ2 has reached a preset number. Athickness of the second film SF2 relies on the repetition number of thesequence SQ2. That is, the thickness of the second film SF2 isdetermined finally and substantially by a product of the repetitionnumber of the sequence SQ2 and a thickness of the silicon oxide filmformed by performing the sequence SQ2 a single time (unit cycle). Thus,the repetition number of the sequence SQ2 may be set based on a requiredthickness of the second film SF2.

If it is determined in the process ST32 e that the repetition number ofthe sequence SQ2 has not reached the preset number (process ST32 e: NO),the sequence SQ2 is repeated. Meanwhile, if it is determined in theprocess ST32 e that the repetition number of the sequence SQ2 hasreached the preset number (process ST32 e: YES), the sequence SQ2 isended. Accordingly, as the sequence SQ2 is repeatedly performed thepreset number of times, the second film SF2 having the requiredthickness may be formed on the first film SF1 (particularly, on theindividual end surfaces of the protrusion regions of the processingtarget layer EL (the end surface TE1 of the protrusion region PJ1, theend surface TE2 of the protrusion region PJ2, and so forth) of the firstfilm SF1).

In the process ST4 (second process) following the process ST3, the film(the first film SF1 and the second film SF2), which is formed throughthe process ST2 and the process ST3, is anisotropically etched in thestate that the wafer W is placed on the electrostatic chuck ESC as shownin FIG. 2. As a result, the corresponding film is partially removed(more specifically, portions of the first film SF1 and the second filmSF2 formed on one or more end surfaces of the protrusion regions of theprocessing target layer EL (for example, on the end surface TE1 of theprotrusion region PJ1 shown in FIG. 5) are removed). That is, in theprocess ST4, by anisotropically etching the film (the first film SF1 andthe second film SF2) formed through the process ST2 and the process ST3,the one or more end surfaces (for example, the end surface TE1 of theprotrusion region PJ1 shown in FIG. 6) are selectively exposed.

The film formed by the process ST2 and the process ST3 has a largerthickness as the height thereof from the main surface BE1 of thesupporting base body BE gets higher. Thus, the lower the height from themain surface BE1 of the supporting base body BE is, the larger theamount of the film removed by the anisotropic etching of the process ST4may be. Accordingly, in the anisotropic etching of the process ST4, byadjusting processing conditions of the process ST4, it is possible toremove only the film (the first film SF1 and the second film SF2) formedon, among the protrusion regions of the processing target layer EL, theend surface of the protrusion having the lowest height from the mainsurface BE1 of the supporting base body BE (e.g., the end surface TE1 ofthe protrusion region PJ1), as illustrated in FIG. 6, for example.Further, in the anisotropic etching of the process ST4, by furtheradjusting the processing conditions of the process ST4, it is possibleto remove only the film (the first film SF1 and the second film SF2)formed, among the protrusion regions of the processing target layer EL,on the respective end surfaces of plural protrusion regions from the(first) protrusion region having the lowest height from the main surfaceBE1 of the supporting base body BE to the n^(th) protrusion region (ndenotes an integer equal to or more than 2, hereinafter) in sequence(e.g., on the respective end surfaces from the end surface TE1 of theprotrusion region PJ1 to the end surface TE2 of the protrusion regionPJ2). As stated above, through the anisotropic etching of the processST4, it is possible to selectively remove only the film (the first filmSF1 and the second film SF2) formed on the end surface, among therespective end surfaces of the plurality of protrusion regions of theprocessing target layer EL, of the protrusion region having the lowestheight from the main surface BE1 of the supporting base body BE or onlythe film (the first film SF1 and the second film SF2) formed on therespective end surfaces of the plural protrusion regions from the(first) protrusion region having the lowest height from the main surfaceBE1 of the supporting base body BE to the n^(th) protrusion region insequence.

The process ST4 will be elaborated. Hereinafter, as the exemplaryembodiment, details of the process ST4 performed in the example casewhere the first film SF1 and the second film SF2 contain the siliconoxide (e.g., the SiO₂ film) will explained. If, however, the first filmSF1 and the second film SF2 contain a film of another material otherthan the silicon oxide film containing the silicon oxide, other kinds ofgases as well as gases specified below can be used. A sixth gas issupplied into the processing space S of the processing vessel 12 from agas source selected from the plurality of gas sources belonging to thegas source group 40. The sixth gas may contain a fluorocarbon-based gas(C_(x)F_(y) such as CF₄, C₄F₈, or CHF₃). The high frequency power issupplied from the first high frequency power supply 62, and the highfrequency bias power is supplied from the second high frequency powersupply 64. Further, the internal pressure of the processing space S ofthe processing vessel 12 is set to a predetermined pressure by operatingthe gas exhaust device 50. As a result, plasma of the sixth gas isgenerated. Fluorine-containing active species in the generated plasmaare attracted in the vertical direction (the surface-perpendiculardirection DR) by the high frequency bias power and anisotropically(primarily) etch portions of the film (the first film SF1 and the secondfilm SF2), which is formed through the process ST2 and the process ST3,provided on the respective end surfaces of the protrusion regions of theprocessing target layer EL. As a result of the anisotropic etching ofthe process ST4, it is possible to selectively expose, among theprotrusion regions of the processing target layer EL, only the endsurface of the protrusion region having the lowest height from the mainsurface BE1 of the supporting base body BE (for example, the end surfaceTE1 of the protrusion region PJ1 shown in FIG. 6), or only therespective end surfaces of the plural protrusion regions from the(first) protrusion region having the lowest height from the main surfaceBE1 of the supporting base body BE to the n^(th) protrusion region insequence (for example, the end surfaces from the end surface TE1 of theprotrusion region PJ1 to the end surface TE2 of the protrusion regionPJ2). By the etching of the process ST4, the second film SF2 formed onthe end surface TE2 of the protrusion region PJ2 becomes to have athickness TH2 b, which is obtained after the process ST4 is performed,smaller than the thickness TH2 a of the second film SF2, which isobtained before the process ST4 is performed.

In the process ST5 (third process) following the process ST4, theprocessing target layer EL is anisotropically etched in the state thatthe wafer W is placed on the electrostatic chuck ESC as shown in FIG. 2.In the process ST5, of the surface EL1 of the processing target layerEL, the end surface selectively exposed by the anisotropic etching ofthe process ST4 (for example, the end surface TE1 shown in FIG. 6 andwill sometimes be referred to as “exposed end surface” in the following)is anisotropically etched atomic layer by atomic layer in thesurface-perpendicular direction DR by the same method as the ALE (AtomicLayer Etching) method. Details of the process ST5 is described in FIG.11. As depicted in FIG. 11, the process ST5 includes a process ST5 a(fourteenth process), a process ST5 b (fifteenth process), a process ST5c (sixteenth process), a process ST5 d (seventeenth process), and aprocess ST5 e. The processes ST5 a to ST5 d constitute a sequence SQ3(third sequence). In the process ST5, the sequence SQ3 is performed one(unit cycle) or more times. By repeating the sequence SQ3, the exposedend surface, which is exposed by the process ST4, is removed atomiclayer by atomic layer, so that the anisotropic etching is selectivelyperformed on the corresponding exposed end surface. Hereinafter, as theexemplary embodiment, details of the process ST5 which is performed whenthe first film SF1 and the second film SF2 contain the silicon oxide(e.g., the SiO₂ film) will be discussed. However, when the first filmSF1 and the second film SF2 contain a film of another material besidesthe silicon oxide film containing the silicon oxide, other kinds ofgases as well as gases specified below may also be used.

In the process ST5 a, plasma of a seventh gas is generated in theprocessing space S in which the wafer W is placed, and a mixed layer MXcontaining ions included in the plasma of the seventh gas is formed onthe atomic layer of the exposed end surface of the processing targetlayer EL. By way of example, in the process ST5 a, by applying the highfrequency bias power from the second high frequency power supply 64 tothe plasma of the seventh gas in the surface-perpendicular direction DR,the mixed layer MX containing the ions included in the plasma of theseventh gas can be formed on the atomic layer of the exposed end surfaceof the processing target layer EL.

In the process ST5 a, by supplying the seventh gas into the processingspace S of the processing vessel 12, the plasma of the seventh gas isgenerated. The seventh gas contains hydrogen atoms and oxygen atoms and,specifically, may contain a mixed gas of a H₂ gas and an O₂ gas. Toelaborate, the seventh gas is supplied into the processing space S ofthe processing vessel 12 from a gas source selected from the pluralityof gas sources belonging to the gas source group 40. Then, the highfrequency power is supplied from the first high frequency power supply62, and the high frequency bias power is supplied from the second highfrequency power supply 64. The internal pressure of the processing spaceS of the processing vessel 12 is set to a predetermined pressure byoperating the gas exhaust device 50. The plasma of the seventh gas isgenerated in the processing space S of the processing vessel 12. As ions(ions of the hydrogen atoms) included in the plasma of the seventh gasare attracted in the vertical direction (in the surface-perpendiculardirection DR) by the high frequency bias power supplied from the secondhigh frequency power supply 64, the ions are brought into contact withthe exposed end surface of the processing target layer EL, so that theexposed end surface is anisotropically modified. As stated above, byapplying the high frequency bias power to the plasma of the seventh gasfrom the second high frequency power supply 64, the mixed layer MXcontaining the ions included in the plasma of the seventh gas is formedon the exposed end surface which is exposed through the process ST4. Inthe process ST5 a, of the surface EL1 of the processing target layer EL(specifically, the respective end surfaces of the protrusion regions ofthe processing target layer EL), the anisotropically modified portionbecomes the mixed layer MX.

FIG. 13A to FIG. 13C are diagrams illustrating a principle of theetching in the method (sequence SQ3) shown in FIG. 11. In FIG. 13A toFIG. 13C, empty circles (white circles) represent atoms constituting theprocessing target layer EL (for example, atoms constituting SiN);black-colored circles (black circles) indicate the ions (ions ofhydrogen atoms) contained in the plasma of the seventh gas; andencircled ‘x’ marks indicate radicals included in plasma of an eighthgas to be described later. As depicted in FIG. 13A, through the processST5 a, the ions (black-colored circles (black circles)) of the hydrogenatoms included in the plasma of the seventh gas are anisotropicallysupplied to the atomic layer of the exposed end surface of theprocessing target layer EL in the surface-perpendicular direction DR.Accordingly, through the process ST5 a, the mixed layer MX containingthe atoms constituting the processing target layer EL and the hydrogenatoms of the seventh gas is formed on the atomic layer of the exposedend surface of the processing target layer EL, as shown in FIG. 7.

In the process ST5 b following the process ST5 a, the processing space Sof the processing vessel 12 is purged. To elaborate, the seventh gassupplied in the process ST5 a is exhausted. In the process ST5 b, aninert gas such as a rare gas (e.g., an Ar gas or the like) may besupplied into the processing vessel 12 as a purge gas. That is, thepurging of the process ST5 b may be implemented by the gas purging ofallowing the inert gas to flow in the processing space S of theprocessing vessel 12 or the purging by vacuum evacuation.

In the process ST5 c following the process ST5 b, the plasma of theeighth gas is generated in the processing space S of the processingvessel 12, and the mixed layer MX is removed by radicals included in theplasma (that is, by chemical etching using the corresponding radicals).The plasma of the eighth gas generated in the process ST5 c includes theradicals for removing the mixed layer MX. The encircled ‘x’ marks shownin FIG. 13B indicate the radicals included in the plasma of the eighthgas. The eighth gas contains fluorine atoms. By way of non-limitingexample, the eighth gas may include a mixed gas containing a NF₃ gas andan O₂ gas. Alternatively, the eighth gas may include a mixed gascontaining the NF₃ gas and a H₂ gas. To be more specific, the eighth gasis supplied into the processing space S of the processing vessel 12 froma gas source selected from the plurality of gas sources belonging to thegas source group 40. The high frequency power is supplied from the firsthigh frequency power supply 62, and the high frequency bias power issupplied from the second high frequency power supply 64. By operatingthe gas exhaust device 50, the internal pressure of the processing spaceS of the processing vessel 12 is set to a predetermined pressure. As aresult, the plasma of the eighth gas is generated in the processingspace S of the processing vessel 12. The radicals in the plasma of theeighth gas generated in the process ST5 c come into contact with themixed layer MX. As depicted in FIG. 13B, through the process ST5 c, asthe radicals of the atoms of the eighth gas are supplied to the mixedlayer MX, the mixed layer MX is chemically etched to be removed from theprocessing target layer EL.

As stated above, as shown in FIG. 8 and FIG. 13C, in the process ST5 c,the mixed layer MX formed through the process ST5 a can be removed fromthe exposed end surface of the processing target layer EL by theradicals included in the plasma of the eighth gas.

In the process ST5 d following the process ST5 c, the processing space Sof the processing vessel 12 is purged. To elaborate, the eighth gassupplied in the process ST5 c is exhausted. In the process ST5 d, aninert gas such as a rare gas (e.g., an Ar gas or the like) may besupplied into the processing vessel 12 as a purge gas. That is, thepurging of the process ST5 d may be implemented by the gas purging ofallowing the inert gas to flow in the processing space S of theprocessing vessel 12 or the purging by vacuum evacuation.

In the process ST5 e following the sequence SQ3, it is determinedwhether or not to finish the repetition of the sequence SQ3. Toelaborate, in the process ST5 e, it is determined whether the repetitionnumber of the sequence SQ3 has reached a preset number. An etchingamount upon the exposed end surface of the processing target layer EL(that is, a depth of a groove formed in the corresponding exposed endsurface of the processing target layer EL by the etching) relies on therepetition number of the sequence SQ3. The sequence SQ3 may be repeatedsuch that the exposed end surface of the processing target layer EL isetched until the etching amount upon the exposed end surface of theprocessing target layer EL reaches a preset value. As the repetitionnumber of the sequence SQ3 is increased, the etching amount upon theexposed end surface of the processing target layer EL is increased (in asubstantially linear manner). Thus, the repetition number of thesequence SQ3 may be determined such that a value obtained by a productof a thickness etched by performing the sequence SQ3 a single time (unitcycle) (thickness of the mixed layer MX formed by performing the processST5 a a single time) and the repetition number of the sequence SQ3reaches a predetermined value.

If it is determined in the process ST5 e that the repetition number ofthe sequence SQ3 has not reached the preset number (process ST5 e: NO),the sequence SQ3 is repeated. Meanwhile, if it is determined in theprocess ST5 e that the repetition number of the sequence SQ3 has reachedthe preset number (process ST5 e: YES), the sequence SQ3 is ended.

Through the series of processes from the sequence SQ3 to the process ST5e, the anisotropic etching can be selectively performed only on theexposed end surface of the processing target layer EL, which is exposedin the process ST4, atomic layer by atomic layer with high accuracythrough the same method as the ALE method.

In the exemplary embodiment, the etching processing performed after theprocess ST4 is implemented by the process ST5. However, the exemplaryembodiment is not limited thereto, and various other kinds of etchingprocessings may be used. By way of example, an etching processing ofperforming the same processing sequence as the process ST5 by using agas different from the gas used in the process ST5, an etchingprocessing using CW (continuous discharge), an etching processingthrough isotropic etching, or the like may be performed after theprocess ST4.

In the method MT according to the exemplary embodiment as describedabove, on the protrusion regions (the protrusion region PJ1, theprotrusion region PJ2, and so forth) of the processing target layer ELeach having the end surface, the film (the first film SF1 and the secondfilm SF2) is formed on the respective end surfaces (the end surface TE1,the end surface TE2, and so forth) through the process ST2 and theprocess ST3. Then, only the film on the one or more end surfaces (forexample, the end surface TE1 of the protrusion region PJ1) isselectively removed through the process ST4, and the corresponding oneor more end surfaces exposed through the removal of the film in theprocess ST4 is anisotropically etched atomic layer by atomic layerthrough the process ST5. Accordingly, the anisotropic etching can beperformed with high accuracy only on the one or more end surfaces amongthe respective end surfaces of the protrusion regions.

The thickness of the film formed through the process ST2 and the processST3 is different depending on the distance from the main surface BE1 ofthe supporting base body BE. Thus, the end surface, on which the film isformed in a relatively thin thickness, is selectively exposed throughthe process ST4.

Through the process ST2, the first film SF1 of the silicon oxide filmhaving a uniform thickness is conformally formed on the respective endsurfaces of the protrusion regions of the processing target layer EL inthe exemplary embodiment.

Through the process ST2 a, the reaction precursor of the silicon can beformed by using the first gas containing the monoaminosilane in theexemplary embodiment.

Through the process ST2 a, the aminosilane having the one to threesilicon atoms can be used as the aminosilane-based gas included in thefirst gas in the exemplary embodiment. Further, the aminosilane havingthe one to three amino groups can be used as the aminosilane-based gasincluded in the first gas in the exemplary embodiment.

Through the process ST31 (process ST3), with the plasma of the third gascontaining the silicon atoms and containing the chlorine atoms or thehydrogen atoms, for example, the third gas containing the SiCl₄ gas orthe SiH₄ gas, the second film SF2 of the silicon oxide film can beadditionally formed on the first film SF1 of the silicon oxide film,which is conformally formed in the process ST2 prior to the process ST3,in the exemplary embodiment.

Through the process ST32 (process ST3), the sequence SQ2 including theprocess ST32 a using the fourth gas containing the silicon atoms and thechlorine atoms, for example, the fourth gas containing the mixed gas ofthe SiCl₄ and the Ar gas and including the process ST32 c using theplasma of the fifth gas containing the oxygen atoms is repeated. As aresult, the second film SF2 of the silicon oxide film can beadditionally formed on the first film SF1 of the silicon oxide film,which is conformally formed in the process ST2 prior to the process ST3,in the exemplary embodiment.

Through the process ST4, the end surface, on which the film having therelatively thin thickness is provided, is selectively exposed throughthe anisotropic etching with the plasma of the fluorocarbon-based gas inthe exemplary embodiment.

Through the process ST5, the end surface exposed through the process ST4is modified atomic layer by atomic layer, so that the mixed layer isformed in the process ST5 a. Further, this modified region(corresponding to the mixed layer MX) modified through the process ST5 acan be removed in the process ST5 c. Thus, as the sequence SQ3 includingthe process ST5 a and the process ST5 c is repeated, the end surfaceexposed through the process ST4 is selectively etched to a requiredextent.

Through the process ST5 a, the mixed layer MX is selectively formed onthe atomic layer of the end surface exposed through the process ST4 byapplying the bias power to the seventh gas.

Through the process ST5 c, the mixed layer formed through the processST5 a is removed by using the plasma of the eighth gas containing themixed gas of the NF₃ gas and the O₂ gas in the exemplary embodiment.

From the foregoing, it will be appreciated that the exemplary embodimentof the present disclosure has been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the embodiment disclosed herein is not intended to belimiting. The scope of the inventive concept is defined by the followingclaims and their equivalents rather than by the detailed description ofthe exemplary embodiment. It shall be understood that all modificationsand embodiments conceived from the meaning and scope of the claims andtheir equivalents are included in the scope of the inventive concept.

By way of example, the kinds of the first to eighth gases may not belimited to those specified in the above-described exemplary embodiment,and various other kinds of gases capable of achieving the same effectsas those of the above-described exemplary embodiment can be usedinstead. Furthermore, the material of the processing target layer EL isnot limited to the one specified in the exemplary embodiment, andvarious other kinds of materials having the same effects as those of theexemplary embodiment can be used instead.

We claim:
 1. An etching method of etching a processing target objecthaving a supporting base body and a processing target layer, theprocessing target layer being provided on a main surface of thesupporting base body and including protrusion regions, each of theprotrusion regions being extended upwards from the main surface, and anend surface of each of the protrusion regions being exposed when viewedfrom above the main surface, the etching method comprising: a firstprocess of forming a film on the end surface of each of the protrusionregions; a second process of selectively exposing one or more of the endsurfaces by anisotropically etching the film formed through the firstprocess; and a third process of anisotropically etching the one or moreof the end surfaces exposed through the second process by atomic layeretching, wherein the processing target layer contains silicon nitride,and the film contains silicon oxide.
 2. The etching method of claim 1,wherein the film comprises a first film and a second film, the firstprocess comprises a fourth process of forming the first film conformallyand a fifth process of forming the second film on the first film, andthe second film is formed in the fifth process such that a thickness ofthe second film is increased as being distanced farther from the mainsurface.
 3. The etching method of claim 2, wherein the first film isconformally formed in the fourth process by repeating a first sequencecomprising: a sixth process of supplying a first gas into a space inwhich the processing target object is placed; a seventh process ofpurging, after the sixth process, the space in which the processingtarget object is placed; an eighth process of generating, after theseventh process, plasma of a second gas in the space in which theprocessing target object is placed; and a ninth process of purging,after the eighth process, the space in which the processing targetobject is placed, wherein the first gas contains an organic-containingaminosilane-based gas, the second gas contains oxygen atoms, and plasmaof the first gas is not generated in the sixth process.
 4. The etchingmethod of claim 3, wherein the first gas contains monoaminosilane. 5.The etching method of claim 3, wherein the aminosilane-based gascontained in the first gas includes aminosilane having one to threesilicon atoms.
 6. The etching method of claim 3, wherein theaminosilane-based gas contained in the first gas includes aminosilanehaving one to three amino groups.
 7. The etching method of claim 2,wherein, in the fifth process, plasma of a third gas is generated in aspace in which the processing target object is placed, and the third gascontains silicon atoms and contains chlorine atoms or hydrogen atoms. 8.The etching method of claim 7, wherein the third gas includes a SiCl₄gas or a SiH₄ gas.
 9. The etching method of claim 2, wherein the secondfilm is formed in the fifth process by repeating a second sequencecomprising: a tenth process of supplying a fourth gas into a space inwhich the processing target object is placed; an eleventh process ofpurging, after the tenth process, the space in which the processingtarget object is placed; a twelfth process of generating, after theeleventh process, plasma of a fifth gas in the space in which theprocessing target object is placed; and a thirteenth process of purging,after the twelfth process, the space in which the processing targetobject is placed, wherein the fourth gas contains silicon atoms andchlorine atoms, the fifth gas contains oxygen atoms, and plasma of thefourth gas is not generated in the tenth process.
 10. The etching methodof claim 9, wherein the fourth gas includes a mixed gas containing aSiCl₄ gas and an Ar gas.
 11. The etching method of claim 1, wherein, inthe second process, plasma of a sixth gas is generated in a space inwhich the processing target object is placed and a bias power is appliedto the plasma of the sixth gas, and the sixth gas contains afluorocarbon-based gas.
 12. The etching method of claim 1, wherein theone or more of the end surfaces exposed through the second process areremoved by atomic layer etching to be selectively and anisotropicallyetched by repeating a third sequence comprising: a fourteenth process ofgenerating plasma of a seventh gas in a space in which the processingtarget object is placed and forming a mixed layer containing ionsincluded in the plasma of the seventh gas on an atomic layer of the oneor more of the end surfaces exposed through the second process, afifteenth process of purging, after the fourteenth process, the space inwhich the processing target object is placed, a sixteenth process ofgenerating, after the fifteenth process, plasma of an eighth gas in thespace in which the processing target object is placed and removing themixed layer by radicals included in the plasma of the eighth gas; and aseventeenth process of purging, after the sixteenth process, the spacein which the processing target object is placed, the seventh gascontains hydrogen atoms or oxygen atoms, and the eighth gas containsfluorine atoms.
 13. The etching method of claim 12, wherein, in thefourteenth process, by applying a bias power to the plasma of theseventh gas, the mixed layer containing the ions is formed on the atomiclayer of the one or more of the end surfaces exposed through the secondprocess.
 14. The etching method of claim 12, wherein the eighth gasincludes a mixed gas containing a NF₃ gas and an O₂ gas.
 15. An etchingmethod of etching a target object, the etching method comprising:providing the target object having a supporting base and a target layer,the target layer being provided on a main surface of the supporting baseand including protruding regions, each of the protruding regions beingextended upwards from the main surface, and an end surface of each ofthe protruding regions being exposed; forming a film on the end surfaceof each of the protruding regions; anisotropically etching the film toselectively expose one or more of the end surfaces; and anisotropicallyetching the one or more of the end surfaces by atomic layer etching. 16.The etching method of claim 15, wherein the target layer includessilicon nitride, and wherein the film includes silicon oxide.